You could go to brave://rewards-internals and in general info tab check what region you selected. Do tell me your region.
Also, Gemini is now supported in the US only, so if you’re not from there. This issue will arise. This issue arises only when the brave rewards profile is a new one. Like, you installed brave newly on the device, reset brave rewards or reset the app or uninstall and install it.
This will not affect your already connected rewards profiles.
You’ll find more details above.